This invention relates to a method and apparatus for measuring the tensile bond strength between one end of a polymer rod and a flat substrate.
In the search for suitable materials which will be competitive with metals in articles of manufacture that utilize molding techniques during one of the manufacturing stages, it is desirable to find a material which has a high modulus of elasticity, a high degree of toughness, and which is suitable for low cost injection molding processes. Two possible candidates are epoxy resin composites and thermoplastic or polymer composites. With epoxy resin composites, strong adhesion to a substrate is virtually assured, but in the area of thermoplastic or polymer composites, weak bonds are to be anticipated. Since thermoplastic composites may be developed much more cheaply than epoxy resin composites, it is desirable to qualitatively and quantitatively measure the pertinent parameters of the former.
Design of reinforced polymer composites requires knowledge of the strength of bond between a mineral filler surface and a polymer matrix. In prior art methods, this may be somewhat laboriously determined by testing the composites in their final use conditions. However, this is a time consuming process, unsuitable for screening a host of parameters affecting the adhesion process. It is desirable, therefore, to develop a testing method that would permit rapid simulation of the essential conditions present during bond formation in an actual composite, in a short period of time. This would have the advantage of enabling one to measure the tensile strength of a bond reproducibly under controlled conditions. Numerous areas of interest would benefit from such a method. For example, it may be desirable to screen certain surface-chemical agents which are reputed to have adhesion promoting properties but for which no adhesion test data is available for the system of interest, viz., a silicate mineral in a polypropylene matrix. Another application would be testing of microscopic polymer/filler dispersions, such as fine vermiculite flakes in a polycarbonate matrix. Other areas where methods of this nature would be particularly useful are the evaluation of surface preparation techniques and optimization of temperature-time aging treatments in polymer-inter layer systems.